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# Network configuration
menu "Networking support"
config NET
bool "Networking support"
Unless you really know what you are doing, you should say Y here.
The reason is that some programs need kernel networking support even
when running on a stand-alone machine that isn't connected to any
other computer. If you are upgrading from an older kernel, you
should consider updating your networking tools too because changes
in the kernel and the tools often go hand in hand. The tools are
contained in the package net-tools, the location and version number
of which are given in <file:Documentation/Changes>.
For a general introduction to Linux networking, it is highly
recommended to read the NET-HOWTO, available from
menu "Networking options"
depends on NET
config PACKET
tristate "Packet socket"
The Packet protocol is used by applications which communicate
directly with network devices without an intermediate network
protocol implemented in the kernel, e.g. tcpdump. If you want them
to work, choose Y.
To compile this driver as a module, choose M here: the module will
be called af_packet.
If unsure, say Y.
bool "Packet socket: mmapped IO"
depends on PACKET
If you say Y here, the Packet protocol driver will use an IO
mechanism that results in faster communication.
If unsure, say N.
config UNIX
tristate "Unix domain sockets"
If you say Y here, you will include support for Unix domain sockets;
sockets are the standard Unix mechanism for establishing and
accessing network connections. Many commonly used programs such as
the X Window system and syslog use these sockets even if your
machine is not connected to any network. Unless you are working on
an embedded system or something similar, you therefore definitely
want to say Y here.
To compile this driver as a module, choose M here: the module will be
called unix. Note that several important services won't work
correctly if you say M here and then neglect to load the module.
Say Y unless you know what you are doing.
config NET_KEY
tristate "PF_KEY sockets"
select XFRM
PF_KEYv2 socket family, compatible to KAME ones.
They are required if you are going to use IPsec tools ported
from KAME.
Say Y unless you know what you are doing.
config INET
bool "TCP/IP networking"
These are the protocols used on the Internet and on most local
Ethernets. It is highly recommended to say Y here (this will enlarge
your kernel by about 144 KB), since some programs (e.g. the X window
system) use TCP/IP even if your machine is not connected to any
other computer. You will get the so-called loopback device which
allows you to ping yourself (great fun, that!).
For an excellent introduction to Linux networking, please read the
Linux Networking HOWTO, available from
If you say Y here and also to "/proc file system support" and
"Sysctl support" below, you can change various aspects of the
behavior of the TCP/IP code by writing to the (virtual) files in
/proc/sys/net/ipv4/*; the options are explained in the file
Short answer: say Y.
source "net/ipv4/Kconfig"
# IPv6 as module will cause a CRASH if you try to unload it
config IPV6
tristate "The IPv6 protocol"
depends on INET
default m
This is complemental support for the IP version 6.
You will still be able to do traditional IPv4 networking as well.
For general information about IPv6, see
For Linux IPv6 development information, see <>.
For specific information about IPv6 under Linux, read the HOWTO at
To compile this protocol support as a module, choose M here: the
module will be called ipv6.
source "net/ipv6/Kconfig"
menuconfig NETFILTER
bool "Network packet filtering (replaces ipchains)"
Netfilter is a framework for filtering and mangling network packets
that pass through your Linux box.
The most common use of packet filtering is to run your Linux box as
a firewall protecting a local network from the Internet. The type of
firewall provided by this kernel support is called a "packet
filter", which means that it can reject individual network packets
based on type, source, destination etc. The other kind of firewall,
a "proxy-based" one, is more secure but more intrusive and more
bothersome to set up; it inspects the network traffic much more
closely, modifies it and has knowledge about the higher level
protocols, which a packet filter lacks. Moreover, proxy-based
firewalls often require changes to the programs running on the local
clients. Proxy-based firewalls don't need support by the kernel, but
they are often combined with a packet filter, which only works if
you say Y here.
You should also say Y here if you intend to use your Linux box as
the gateway to the Internet for a local network of machines without
globally valid IP addresses. This is called "masquerading": if one
of the computers on your local network wants to send something to
the outside, your box can "masquerade" as that computer, i.e. it
forwards the traffic to the intended outside destination, but
modifies the packets to make it look like they came from the
firewall box itself. It works both ways: if the outside host
replies, the Linux box will silently forward the traffic to the
correct local computer. This way, the computers on your local net
are completely invisible to the outside world, even though they can
reach the outside and can receive replies. It is even possible to
run globally visible servers from within a masqueraded local network
using a mechanism called portforwarding. Masquerading is also often
called NAT (Network Address Translation).
Another use of Netfilter is in transparent proxying: if a machine on
the local network tries to connect to an outside host, your Linux
box can transparently forward the traffic to a local server,
typically a caching proxy server.
Yet another use of Netfilter is building a bridging firewall. Using
a bridge with Network packet filtering enabled makes iptables "see"
the bridged traffic. For filtering on the lower network and Ethernet
protocols over the bridge, use ebtables (under bridge netfilter
Various modules exist for netfilter which replace the previous
masquerading (ipmasqadm), packet filtering (ipchains), transparent
proxying, and portforwarding mechanisms. Please see
<file:Documentation/Changes> under "iptables" for the location of
these packages.
Make sure to say N to "Fast switching" below if you intend to say Y
here, as Fast switching currently bypasses netfilter.
Chances are that you should say Y here if you compile a kernel which
will run as a router and N for regular hosts. If unsure, say N.
bool "Network packet filtering debugging"
depends on NETFILTER
You can say Y here if you want to get additional messages useful in
debugging the netfilter code.
bool "Bridged IP/ARP packets filtering"
depends on BRIDGE && NETFILTER && INET
default y
Enabling this option will let arptables resp. iptables see bridged
ARP resp. IP traffic. If you want a bridging firewall, you probably
want this option enabled.
Enabling or disabling this option doesn't enable or disable
If unsure, say N.
source "net/ipv4/netfilter/Kconfig"
source "net/ipv6/netfilter/Kconfig"
source "net/decnet/netfilter/Kconfig"
source "net/bridge/netfilter/Kconfig"
config XFRM
depends on NET
source "net/xfrm/Kconfig"
source "net/sctp/Kconfig"
config ATM
tristate "Asynchronous Transfer Mode (ATM) (EXPERIMENTAL)"
ATM is a high-speed networking technology for Local Area Networks
and Wide Area Networks. It uses a fixed packet size and is
connection oriented, allowing for the negotiation of minimum
bandwidth requirements.
In order to participate in an ATM network, your Linux box needs an
ATM networking card. If you have that, say Y here and to the driver
of your ATM card below.
Note that you need a set of user-space programs to actually make use
of ATM. See the file <file:Documentation/networking/atm.txt> for
further details.
config ATM_CLIP
tristate "Classical IP over ATM (EXPERIMENTAL)"
depends on ATM && INET
Classical IP over ATM for PVCs and SVCs, supporting InARP and
ATMARP. If you want to communication with other IP hosts on your ATM
network, you will typically either say Y here or to "LAN Emulation
(LANE)" below.
bool "Do NOT send ICMP if no neighbour (EXPERIMENTAL)"
depends on ATM_CLIP
Normally, an "ICMP host unreachable" message is sent if a neighbour
cannot be reached because there is no VC to it in the kernel's
ATMARP table. This may cause problems when ATMARP table entries are
briefly removed during revalidation. If you say Y here, packets to
such neighbours are silently discarded instead.
config ATM_LANE
tristate "LAN Emulation (LANE) support (EXPERIMENTAL)"
depends on ATM
LAN Emulation emulates services of existing LANs across an ATM
network. Besides operating as a normal ATM end station client, Linux
LANE client can also act as an proxy client bridging packets between
ELAN and Ethernet segments. You need LANE if you want to try MPOA.
config ATM_MPOA
tristate "Multi-Protocol Over ATM (MPOA) support (EXPERIMENTAL)"
depends on ATM && INET && ATM_LANE!=n
Multi-Protocol Over ATM allows ATM edge devices such as routers,
bridges and ATM attached hosts establish direct ATM VCs across
subnetwork boundaries. These shortcut connections bypass routers
enhancing overall network performance.
config ATM_BR2684
tristate "RFC1483/2684 Bridged protocols"
depends on ATM && INET
ATM PVCs can carry ethernet PDUs according to rfc2684 (formerly 1483)
This device will act like an ethernet from the kernels point of view,
with the traffic being carried by ATM PVCs (currently 1 PVC/device).
This is sometimes used over DSL lines. If in doubt, say N.
config ATM_BR2684_IPFILTER
bool "Per-VC IP filter kludge"
depends on ATM_BR2684
This is an experimental mechanism for users who need to terminating a
large number of IP-only vcc's. Do not enable this unless you are sure
you know what you are doing.
config BRIDGE
tristate "802.1d Ethernet Bridging"
If you say Y here, then your Linux box will be able to act as an
Ethernet bridge, which means that the different Ethernet segments it
is connected to will appear as one Ethernet to the participants.
Several such bridges can work together to create even larger
networks of Ethernets using the IEEE 802.1 spanning tree algorithm.
As this is a standard, Linux bridges will cooperate properly with
other third party bridge products.
In order to use the Ethernet bridge, you'll need the bridge
configuration tools; see <file:Documentation/networking/bridge.txt>
for location. Please read the Bridge mini-HOWTO for more
If you enable iptables support along with the bridge support then you
turn your bridge into a bridging IP firewall.
iptables will then see the IP packets being bridged, so you need to
take this into account when setting up your firewall rules.
Enabling arptables support when bridging will let arptables see
bridged ARP traffic in the arptables FORWARD chain.
To compile this code as a module, choose M here: the module
will be called bridge.
If unsure, say N.
config VLAN_8021Q
tristate "802.1Q VLAN Support"
Select this and you will be able to create 802.1Q VLAN interfaces
on your ethernet interfaces. 802.1Q VLAN supports almost
everything a regular ethernet interface does, including
firewalling, bridging, and of course IP traffic. You will need
the 'vconfig' tool from the VLAN project in order to effectively
use VLANs. See the VLAN web page for more information:
To compile this code as a module, choose M here: the module
will be called 8021q.
If unsure, say N.
config DECNET
tristate "DECnet Support"
The DECnet networking protocol was used in many products made by
Digital (now Compaq). It provides reliable stream and sequenced
packet communications over which run a variety of services similar
to those which run over TCP/IP.
To find some tools to use with the kernel layer support, please
look at Patrick Caulfield's web site:
More detailed documentation is available in
Be sure to say Y to "/proc file system support" and "Sysctl support"
below when using DECnet, since you will need sysctl support to aid
in configuration at run time.
The DECnet code is also available as a module ( = code which can be
inserted in and removed from the running kernel whenever you want).
The module is called decnet.
source "net/decnet/Kconfig"
source "net/llc/Kconfig"
config IPX
tristate "The IPX protocol"
select LLC
This is support for the Novell networking protocol, IPX, commonly
used for local networks of Windows machines. You need it if you
want to access Novell NetWare file or print servers using the Linux
Novell client ncpfs (available from
<>) or from
within the Linux DOS emulator DOSEMU (read the DOSEMU-HOWTO,
available from <>). In order
to do the former, you'll also have to say Y to "NCP file system
support", below.
IPX is similar in scope to IP, while SPX, which runs on top of IPX,
is similar to TCP. There is also experimental support for SPX in
Linux (see "SPX networking", below).
To turn your Linux box into a fully featured NetWare file server and
IPX router, say Y here and fetch either lwared from
<> or
mars_nwe from <>. For more
information, read the IPX-HOWTO available from
General information about how to connect Linux, Windows machines and
Macs is on the WWW at <>.
The IPX driver would enlarge your kernel by about 16 KB. To compile
this driver as a module, choose M here: the module will be called ipx.
Unless you want to integrate your Linux box with a local Novell
network, say N.
source "net/ipx/Kconfig"
config ATALK
tristate "Appletalk protocol support"
select LLC
AppleTalk is the protocol that Apple computers can use to communicate
on a network. If your Linux box is connected to such a network and you
wish to connect to it, say Y. You will need to use the netatalk package
so that your Linux box can act as a print and file server for Macs as
well as access AppleTalk printers. Check out
<> on the WWW for details.
EtherTalk is the name used for AppleTalk over Ethernet and the
cheaper and slower LocalTalk is AppleTalk over a proprietary Apple
network using serial links. EtherTalk and LocalTalk are fully
supported by Linux.
General information about how to connect Linux, Windows machines and
Macs is on the WWW at <>. The
NET-3-HOWTO, available from
<>, contains valuable
information as well.
To compile this driver as a module, choose M here: the module will be
called appletalk. You almost certainly want to compile it as a
module so you can restart your AppleTalk stack without rebooting
your machine. I hear that the GNU boycott of Apple is over, so
even politically correct people are allowed to say Y here.
source "drivers/net/appletalk/Kconfig"
config X25
tristate "CCITT X.25 Packet Layer (EXPERIMENTAL)"
X.25 is a set of standardized network protocols, similar in scope to
frame relay; the one physical line from your box to the X.25 network
entry point can carry several logical point-to-point connections
(called "virtual circuits") to other computers connected to the X.25
network. Governments, banks, and other organizations tend to use it
to connect to each other or to form Wide Area Networks (WANs). Many
countries have public X.25 networks. X.25 consists of two
protocols: the higher level Packet Layer Protocol (PLP) (say Y here
if you want that) and the lower level data link layer protocol LAPB
(say Y to "LAPB Data Link Driver" below if you want that).
You can read more about X.25 at <> and
Information about X.25 for Linux is contained in the files
<file:Documentation/networking/x25.txt> and
One connects to an X.25 network either with a dedicated network card
using the X.21 protocol (not yet supported by Linux) or one can do
X.25 over a standard telephone line using an ordinary modem (say Y
to "X.25 async driver" below) or over Ethernet using an ordinary
Ethernet card and the LAPB over Ethernet (say Y to "LAPB Data Link
Driver" and "LAPB over Ethernet driver" below).
To compile this driver as a module, choose M here: the module
will be called x25. If unsure, say N.
config LAPB
tristate "LAPB Data Link Driver (EXPERIMENTAL)"
Link Access Procedure, Balanced (LAPB) is the data link layer (i.e.
the lower) part of the X.25 protocol. It offers a reliable
connection service to exchange data frames with one other host, and
it is used to transport higher level protocols (mostly X.25 Packet
Layer, the higher part of X.25, but others are possible as well).
Usually, LAPB is used with specialized X.21 network cards, but Linux
currently supports LAPB only over Ethernet connections. If you want
to use LAPB connections over Ethernet, say Y here and to "LAPB over
Ethernet driver" below. Read
<file:Documentation/networking/lapb-module.txt> for technical
To compile this driver as a module, choose M here: the
module will be called lapb. If unsure, say N.
bool "Frame Diverter (EXPERIMENTAL)"
The Frame Diverter allows you to divert packets from the
network, that are not aimed at the interface receiving it (in
promisc. mode). Typically, a Linux box setup as an Ethernet bridge
with the Frames Diverter on, can do some *really* transparent www
caching using a Squid proxy for example.
This is very useful when you don't want to change your router's
config (or if you simply don't have access to it).
The other possible usages of diverting Ethernet Frames are
- reroute smtp traffic to another interface
- traffic-shape certain network streams
- transparently proxy smtp connections
- etc...
For more informations, please refer to:
If unsure, say N.
config ECONET
tristate "Acorn Econet/AUN protocols (EXPERIMENTAL)"
Econet is a fairly old and slow networking protocol mainly used by
Acorn computers to access file and print servers. It uses native
Econet network cards. AUN is an implementation of the higher level
parts of Econet that runs over ordinary Ethernet connections, on
top of the UDP packet protocol, which in turn runs on top of the
Internet protocol IP.
If you say Y here, you can choose with the next two options whether
to send Econet/AUN traffic over a UDP Ethernet connection or over
a native Econet network card.
To compile this driver as a module, choose M here: the module
will be called econet.
bool "AUN over UDP"
depends on ECONET
Say Y here if you want to send Econet/AUN traffic over a UDP
connection (UDP is a packet based protocol that runs on top of the
Internet protocol IP) using an ordinary Ethernet network card.
bool "Native Econet"
depends on ECONET
Say Y here if you have a native Econet network card installed in
your computer.
tristate "WAN router"
Wide Area Networks (WANs), such as X.25, frame relay and leased
lines, are used to interconnect Local Area Networks (LANs) over vast
distances with data transfer rates significantly higher than those
achievable with commonly used asynchronous modem connections.
Usually, a quite expensive external device called a `WAN router' is
needed to connect to a WAN.
As an alternative, WAN routing can be built into the Linux kernel.
With relatively inexpensive WAN interface cards available on the
market, a perfectly usable router can be built for less than half
the price of an external router. If you have one of those cards and
wish to use your Linux box as a WAN router, say Y here and also to
the WAN driver for your card, below. You will then need the
wan-tools package which is available from <>.
Read <file:Documentation/networking/wan-router.txt> for more
To compile WAN routing support as a module, choose M here: the
module will be called wanrouter.
If unsure, say N.
menu "QoS and/or fair queueing"
config NET_SCHED
bool "QoS and/or fair queueing"
When the kernel has several packets to send out over a network
device, it has to decide which ones to send first, which ones to
delay, and which ones to drop. This is the job of the packet
scheduler, and several different algorithms for how to do this
"fairly" have been proposed.
If you say N here, you will get the standard packet scheduler, which
is a FIFO (first come, first served). If you say Y here, you will be
able to choose from among several alternative algorithms which can
then be attached to different network devices. This is useful for
example if some of your network devices are real time devices that
need a certain minimum data flow rate, or if you need to limit the
maximum data flow rate for traffic which matches specified criteria.
This code is considered to be experimental.
To administer these schedulers, you'll need the user-level utilities
from the package iproute2+tc at <>.
That package also contains some documentation; for more, check out
This Quality of Service (QoS) support will enable you to use
Differentiated Services (diffserv) and Resource Reservation Protocol
(RSVP) on your Linux router if you also say Y to "QoS support",
"Packet classifier API" and to some classifiers below. Documentation
and software is at <>.
If you say Y here and to "/proc file system" below, you will be able
to read status information about packet schedulers from the file
The available schedulers are listed in the following questions; you
can say Y to as many as you like. If unsure, say N now.
source "net/sched/Kconfig"
menu "Network testing"
tristate "Packet Generator (USE WITH CAUTION)"
depends on PROC_FS
This module will inject preconfigured packets, at a configurable
rate, out of a given interface. It is used for network interface
stress testing and performance analysis. If you don't understand
what was just said, you don't need it: say N.
Documentation on how to use the packet generator can be found
at <file:Documentation/networking/pktgen.txt>.
To compile this code as a module, choose M here: the
module will be called pktgen.
config NETPOLL
bool "Netpoll support for trapping incoming packets"
default n
depends on NETPOLL
bool "Netpoll traffic trapping"
default n
depends on NETPOLL
def_bool NETPOLL
source "net/ax25/Kconfig"
source "net/irda/Kconfig"
source "net/bluetooth/Kconfig"
source "drivers/net/Kconfig"